Pattern formation, defined as the creation of a predictable arrangement of cell types in space, is the lynchpin of development within metazoans. Pattern formation also occurs in fungi, but very little is known about the mechanisms underlying fungal pattern formation. Because patterns of cells types form during the development of fungal biofilms, an understanding of the mechanisms of fungal pattern formation could lead to better treatment and prevention of pathogenic biofilms. Currently, these biofilms are a leading cause of mortality from hospital- acquired infections. Our long-term objective is to understand the mechanisms underlying pattern formation within colonies of the budding yeast S. cerevisiae. The proposed research initiated with the discoveries that 1) colonies of S. cerevisiae develop sharply defined layers of sporulated cells interspersed with regions of unsporulated cells, 2) cell-to-cell signaling mediated by the Rim101 pathway and alkaline pH are required for this sporulation pattern. The specific goal of the proposal is to determine how signals and signaling pathways regulate pattern formation in colonies. This goal will be accomplished using mutants defective in the Rim101 pathway or in another pathway implicated in colony sporulation (Cell Wall Integrity pathway), and by identifying other mutants defective in colony sporulation. The role of these pathways in sporulation patterns will be determined using genetic assays for cell-to-cell signaling, molecular analysis of pathway activation, and cytological methods for visualizing patterns of sporulation and gene expression within colony sections. PUBLIC HEALTH RELEVANCE: When fungi grow as biofilms on medical devices such as catheters and heart valves, they can be deadly to patients. Central to the pathogenicity of biofilms is the organization of different cell types within this fungal community. In this proposal, colonies of the yeast S. cerevisiae will be used to investigate how communication between cells can lead to organized patterns of cell types within fungal communities.